The invention discloses a
system and method for treating low-rank
coal. The
system comprises a low-rank
coal pulverizing device, a low-rank
coal screening device, a lump coal hot-wind dense-medium sorting device, a pulverized coal hot-wind dense-medium sorting device, a
clean coal pulverizing device, a forming device, a
pyrolysis device and a
waste heat recovery device, wherein the lump coal hot-wind dense-medium sorting device is provided with a lump coal inlet, a first hot wind inlet, a first
solid dense medium inlet and a first
clean coal outlet; the pulverized coal hot-wind dense-medium sorting device is provided with a pulverized coal inlet, a second hot wind inlet, a second
solid dense medium inlet and a second
clean coal outlet; the
pyrolysis device is provided with a feed inlet, a semi-
coke outlet and a
pyrolysis oil gas outlet; the
waste heat recovery device is provided with a semi-
coke inlet and a hot air outlet, the semi-
coke inlet is connected with the pyrolysis device, and the hot air outlet is connected with the first hot wind inlet and the second hot wind inlet. By means of the
system, the
gangue discharging rate of the low-rank coal can be remarkably increased, and therefore the quality and yield of pyrolyzed products in the subsequent pyrolysis process can be improved; moreover, the
energy cost can be obviously lowered by recovering
waste heat generated in the pyrolysis process and applying the waste heat to the
gangue discharging process.